Feed Requirements and Thermal Efficiency

In order to produce 500 kt/y of ethylene some 651 kt/y of ethane is required. However, to allow for process upsets and general operational issues, a feed operating allowance of 5.5% is typically added. The pyrolysis requires 330 kt/y fuel oil for the furnace fuel. Again, an operating allowance, this time of 3.5%, is made. 

The second column gives the corresponding energy of the feed stock and fuel streams in PJ/y. The total feed and fuel required is 1.027 million tonnes (Mt/y) corresponding to 50.2 PJ/y (HHV basis). 

The by-products in producing 500 kt/y ethylene by ethane cracking are 17,000 t/y each of propylene and mixed C4 stream 

000 t/y of pyrolysis gasoline. Moreover, 40,000 t/y methane (fuel gas) is also produced. The total of ethylene and by-products is 651,000 t/y corresponding to the required feed without an operating allowance. 

The total energy of the products is 38.9 PJ/y. This gives a total operating efficiency for the plant of 77.5%. 

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